Method using slit-robo system to treat sarcopenia

ABSTRACT

The present invention relates to a method using a SLIT-ROBO system to treat sarcopenia and, more specifically, to a method comprising administration of a gene selected from among slit1, slit2, slit3, robo1, robo2, and fragments thereof, or a protein expressed from the gene as an effective method for treating a muscle disease or for improving muscular function.

TECHNICAL FIELD

The present application claims priority to and the benefit of Korean Patent Application Nos. 10-2016-0071252 and 10-2017-0013799 filed in the Korean Intellectual Property Office on Jun. 8, 2016 and Jan. 31, 2017, respectively, the entire contents of which are reference documents of the present application.

The present invention relates to a composition using a SLIT-ROBO system for preventing or treating sarcopenia and, more specifically, to a composition comprising a gene selected from among slit1, slit2, slit3, robo1, robo2, and fragments thereof, or a protein expressed from the gene; and/or an activator thereof as an effective ingredient for preventing or treating a muscle disease or for improving muscular function.

BACKGROUND ART

A slit protein is a well-known protein that regulates the movement of neurons and axons during the developmental process of the nervous system. It was known that a Slit protein could interact with a Robo receptor to regulate physiological activity, and serves as a factor that regulates various intracellular processes in various tissues such as heart, lung, kidney, and breast tissues, and as it has been recently reported that a Slit protein plays an important role in the regulation of growth, adhesion ability, and migration ability of cells, it was reported that a Slit protein can participate in the migration in the differentiation of cells and the occurrence and metastasis of cancer. Specifically, it was reported that a Slit protein and a Robo protein are expressed at the embryonic development stage of a vertebrate, and the expression of Slit3, Robo1 and Robo2 proteins is increased in the muscle tissues. The report mentioned that the expression of a Slit3 protein was increased in the myoblasts of hind leg muscle tissues of an embryo, but the protein only might participate in the migration ability and might not be associated with the differentiation of myoblasts.

A human Robo protein is present in the four forms of Robo1, Robo2, Robo3, and Robo4. It was reported that Slit and Robo could play various roles depending on what subtypes bind to each other, but since the role may vary depending on the expressed cells, studies have been actively conducted until now. In this regard, Korean Patent No. 10-1617497 describes that a Slt3 protein can interact with Robo1 or Robo2 to exhibit activity, can induce the differentiation of osteoblasts through the activity, and can increase osteogenesis.

Sarcopenia refers to a condition in which the amount and function of skeletal muscles are reduced. Sarcopenia occurs for various reasons such as aging, hormonal disorders, malnutrition, insufficient physical activity, inflammation and degenerative diseases, and among them, it is known that aging and a lack of sex hormones may be the main reasons for sarcopenia, and as the average life expectancy is increasing globally due to the advancement in medical technology and the development of various therapeutic agents, the aging population is increasing, and accordingly, it is expected that the demand for treatment of sarcopenia will also be continuously increased.

In patients with sarcopenia, due to the disorder in recruitment, activity or proliferation of satellite cells, which are stem cells of myoblasts, the number of myoblasts is decreased and the proliferation and differentiation of myoblasts are decreased, and accordingly, for the muscles of patients with sarcopenia, the size and number of muscle fibers are decreased at the histological level, so that symptoms in which the muscular functions are decreased occur.

As studies on the mechanism of sarcopenia have been actively conducted mainly in the United States and Europe over the past ten years, interest in the clinical importance of sarcopenia has been rapidly increased. In the early studies, the results showed that general weakening, dysfunction and muscle weakness causing deterioration in quality of life accounted for the most part of sarcopenia, but studies recently released have reported that the risk of osteoporotic fracture may be notably increased in addition to the quality of life. Further, chronic diseases such as diabetes and metabolic syndrome, obesity, chronic renal failure, and chronic liver failure are caused in patients with sarcopenia, and ultimately, the mortality rate is also increased, so that sarcopenia has drawn attention as a disease to be appropriately treated.

In the United States, it has been recently reported that the possibility of physical disability in patients with sarcopenia is increased about 1.5 times to about 3.5 times, and as a result, a social cost of 18.5 billion USD per year is caused. According to the Korea National Health and Nutrition Examination Survey, the prevalence of sarcopenia is 42.0% and 42.7% in males and females over 60, respectively, so that sarcopenia is a very common disease, and in particular, it is certain that sacropenia will be an important social issue in the future because Korea has the highest aging rate in the world.

Currently, it is known that exercise, protein and calorie supplementation are useful for sarcopenia, but these therapies are not very useful for the elderly who account for the majority of patients with sarcopenia, so that there is an urgent need for a therapeutic agent against sarcopenia. However, with respect to therapeutic agents currently used against sarcopenia, drugs exhibiting a direct effect on amelioration of muscle loss and enhancement of muscle mass are still at the clinical trial stage, and currently, there is no medicine finally approved by the FDA. For this reason, efforts have been made to develop some of a selective androgen receptor, an activin receptor antagonist, a fast skeletal muscle troponin inhibitor, and the like as therapeutic agents for sarcopenia in order to treat sarcopenia, but the efforts are currently at the stage of initial clinical trials.

According to reports on trends in the therapeutic agent against sarcopenia, it was reported that the global market of the therapeutic agent against sarcopenia was about $10 million (US) in 2010 and would grow to the $20 million (US) scale in 2018 (“Sarcopenia Therapeutics—Pipeline Assessment and Market Forecasts to 2018”, 2011 Nov. 17). Further, the Innovative Medicines Initiative which is a private conservation cooperative body under the EU in 2013 announced that the institute would invest about 50 million euros in the development of a therapeutic agent against elderly sarcopenia as one of the four major health research themes, and the investment project is underway.

Thus, the present inventors made intensive efforts to develop a therapeutic agent capable of directly exhibiting therapeutic effects on sarcopenia, and as a result, the present inventors confirmed that the muscle masses were decreased in Slit protein-deficient mice, a Slit protein binding to a Robo1 or Robo2 receptor, and as a result, the β-catenin binding to the M-cadherin of myoblasts was released via the Slit-Robo system to activate the β-catenin and increase the expression of myogenin, and subsequently, the formation of muscles could be promoted by inducing the differentiation of myoblasts. In addition, in particular, the present inventors confirmed that not only in the case of treatment of a full-length Slit protein, but also when a LRRD2 protein, which is an active fragment thereof, was treated, an increase in muscle mass could be induced by promoting the differentiation of myoblasts, and as a result, a Slit protein, a Robo protein, active fragments thereof, or genes encoding the same could be used as an effective ingredient of a composition for preventing and treating/alleviating sarcopenia, thereby completing the present invention.

PRIOR ART DOCUMENT

(Patent Document 1) KR10-1617497 B1

DISCLOSURE Technical Problem

As described above, the present inventors confirmed that a Slit protein binding to a Robo1 or Robo2 receptor, and as a result, the β-catenin binding to the M-cadherin of myoblasts was released via the Slit-Robo system to activate the β-catenin and increase the expression of myogenin, and subsequently, the formation of muscles could be promoted by inducing the differentiation of myoblasts. Furthermore, the present inventors confirmed that not only in the case of treatment of a full-length Slit protein, but also when an active fragment thereof was treated, an increase in muscle mass could be induced by promoting the differentiation of myoblasts, thereby completing the present invention.

Accordingly, an object of the present invention is to provide a pharmaceutical composition for preventing and treating a muscle disease.

Another object of the present invention is to provide a health functional food or feed additive for preventing and alleviating a muscle disease.

Still another object of the present invention is to provide a cosmetic composition for improving muscular function.

Yet another object of the present invention is to provide a method for detecting a protein for providing information on diagnosis of a muscle disease.

Still yet another object of the present invention is to provide a method for screening a therapeutic agent against a muscle disease.

Technical Solution

In order to achieve the objects, the present invention provides a pharmaceutical composition for preventing and treating a muscle disease, including one protein selected from the group consisting of Slit1, Slit2, Slit3, Robo1, Robo2, and fragments thereof, or a gene encoding the same; and an activator thereof, as an effective ingredient.

A preferred embodiment of the present invention provides a pharmaceutical composition for preventing and treating a muscle disease, including one protein selected from the group consisting of amino acid sequences of the following SEQ ID Nos. 1 to 4, or a gene encoding the same, as an effective ingredient:

a Slit3 protein consisting of an amino acid of SEQ ID No. 1;

a Robo1 protein consisting of an amino acid of SEQ ID No. 2;

a Robo2 protein consisting of an amino acid of SEQ ID No. 3; and

a LRRD2 protein consisting of an amino acid of SEQ ID No. 4.

Further, the present invention provides a method for treating a muscle disease, the method including the steps of: administering one protein selected from the group consisting of Slit1, Slit2, Slit3, Robo1, Robo2, and fragments thereof, or a gene encoding the same to an individual in need thereof.

In addition, the present invention provides a method for treating a muscle disease, the method including the steps of: administering one protein selected from the group consisting of the amino acid sequences of SEQ ID Nos. 1 to 4, or a gene encoding the same to an individual in need thereof.

Furthermore, the present invention provides a method for treating a muscle disease, the method including the steps of: administering an activator of one protein selected from the group consisting of Slit and fragments thereof, or a gene encoding the same to an individual in need thereof.

Further, the present invention provides a method for treating a muscle disease, the method including the steps of: administering an activator of one protein selected from the group consisting of Robo and fragments thereof, or a gene encoding the same to an individual in need thereof.

In addition, the present invention provides a use of one protein selected from the group consisting of Slit1, Slit2, Slit3, Robo1, Robo2, and fragments thereof, or a gene encoding the same for a pharmaceutical composition for preventing and treating a muscle disease.

Furthermore, the present invention provides a use of one protein selected from the group consisting of the amino acid sequences of SEQ ID Nos. 1 to 4, or a gene encoding the same for a pharmaceutical composition for preventing and treating a muscle disease.

Further, the present invention provides a use of an activator of one protein selected from the group consisting of Slit and fragments thereof, or a gene encoding the same for a pharmaceutical composition for preventing and treating a muscle disease.

In addition, the present invention provides a use of an activator of one protein selected from the group consisting of Robo and fragments thereof, or a gene encoding the same for a pharmaceutical composition for preventing and treating a muscle disease.

Furthermore, the present invention provides a health functional food for preventing and alleviating a muscle disease, including one protein selected from the group consisting of Slit1, Slit2, Slit3, Robo1, Robo2, and fragments thereof, or a gene encoding the same; or an activator thereof, as an effective ingredient.

Further, the present invention provides a use of one protein selected from the group consisting of Slit1, Slit2, Slit3, Robo1, Robo2, and fragments thereof, or a gene encoding the same; or an activator thereof for a health functional food for preventing and alleviating a muscle disease.

In addition, the present invention provides a use of one protein selected from the group consisting of the amino acid sequences of SEQ ID Nos. 1 to 4, or a gene encoding the same for a health functional food for preventing and alleviating a muscle disease.

A preferred embodiment of the present invention provides a health functional food for preventing and alleviating a muscle disease, including one protein selected from the group consisting of the amino acid sequences of SEQ ID Nos. 1 to 4, or a gene encoding the same, as an effective ingredient.

Furthermore, the present invention provides a cosmetic composition for improving muscular function, including one protein selected from the group consisting of Slit1, Slit2, Slit3, Robo1, Robo2, and fragments thereof, or a gene encoding the same; or an activator thereof, as an effective ingredient.

Further, the present invention provides a use of one protein selected from the group consisting of Slit1, Slit2, Slit3, Robo1, Robo2, and fragments thereof, or a gene encoding the same; or an activator thereof for a cosmetic composition for improving muscular function.

In addition, the present invention provides a use of one protein selected from the group consisting of the amino acid sequences of SEQ ID Nos. 1 to 4, or a gene encoding the same for a cosmetic composition for improving muscular function.

A preferred embodiment of the present invention provides a cosmetic composition for improving muscular function, including one protein selected from the group consisting of the amino acid sequences of SEQ ID Nos. 1 to 4, or a gene encoding the same, as an effective ingredient.

Furthermore, the present invention provides a feed additive for improving muscular function, including one protein selected from the group consisting of Slit1, Slit2, Slit3, Robo1, Robo2, and fragments thereof, or a gene encoding the same; or an activator thereof, as an effective ingredient.

Further, the present invention provides a use of one protein selected from the group consisting of Slit1, Slit2, Slit3, Robo1, Robo2, and fragments thereof, or a gene encoding the same; or an activator thereof for a feed additive for improving muscular function.

In addition, the present invention provides a use of one protein selected from the group consisting of the amino acid sequences of SEQ ID Nos. 1 to 4, or a gene encoding the same for a feed additive for improving muscular function.

A preferred embodiment of the present invention provides a feed additive for improving muscular function, including one protein selected from the group consisting of the amino acid sequences of SEQ ID Nos. 1 to 4, or a gene encoding the same, as an effective ingredient.

According to a preferred embodiment of the present invention, the Slit3 protein may be expressed from a slit3 gene consisting of a base sequence of SEQ ID No. 5.

According to a preferred embodiment of the present invention, the Robo1 protein may be expressed from a robo1 gene consisting of a base sequence of SEQ ID No. 6.

According to a preferred embodiment of the present invention, the Robo2 protein may be expressed from a robo2 gene consisting of a base sequence of SEQ ID No. 7.

According to a preferred embodiment of the present invention, the LRRD2 protein may be expressed from a gene consisting of a base sequence of SEQ ID No. 8.

According to another preferred embodiment of the present invention, the muscle disease may be a muscle disease caused by muscular function deterioration, muscle wasting, or muscle degeneration, and the muscle degeneration may be one or more selected from the group consisting of atony, muscular atrophy, muscular dystrophy, muscle degeneration, myasthenia, cachexia, and sarcopenia.

In addition, the present application provides a method for detecting a protein for providing information on diagnosis of a muscle disease, the method including the steps of:

i) measuring an expression level of a Slit3 protein consisting of an amino acid sequence of SEQ ID No. 1 from a subject-derived sample which is an experimental group;

ii) comparing the expression level of the Slit3 protein measured in Step i) with an expression level of a Slit3 protein of a normal individual-derived sample which is a control group; and

iii) determining the experimental group as a muscle disease when the expression level of the Slit3 protein of the experimental group compared in Step ii) is decreased as compared to that of the control group.

Furthermore, the present invention provides a method for screening a therapeutic agent against a muscle disease, the method including the steps of:

i) treating a cell line expressing one or more selected from the group consisting of a Slit3 protein consisting of an amino acid sequence of SEQ ID No. 1, a Robo1 protein consisting of an amino acid sequence of SEQ ID No. 2, and a Robo2 protein consisting of an amino acid sequence of SEQ ID No. 3 with a subject compound or composition;

ii) measuring an expression degree of the Slit3 protein or activity of the Robo1 protein or Robo2 protein in the cell line treated in Step i); and

iii) selecting a subject compound or composition in which the expression degree of the Slit3 or the activity of the Robo1 protein or Robo2 protein in Step ii) is increased in comparison with that of the control group cell line which is not treated with the subject compound or composition.

Advantageous Effects

The present invention can provide a composition for preventing or treating sarcopenia, using a SLIT-ROBO system. In particular, the present invention can provide a composition for preventing and treating a muscle disease, or improving muscular function, containing a gene selected from slit1, slit2, slit3, robo1, robo2, and fragments thereof, or a protein expressing the same; or an activator thereof.

In particular, specifically, the Slit protein of the present invention can bind to a Robo1 or Robo2 receptor to release the β-catenin binding to the M-cadherin of myoblasts via the Slit-Robo system, thereby promoting the formation of muscles by activating the bound β-catenin and increasing the expression of myogenin to induce the differentiation of myoblasts. Further, not only in the case of treatment of a full-length Slit protein, but also when an active fragment thereof, particularly preferably, a LRRD2 protein is treated, an increase in muscle mass can be induced by promoting the differentiation of myoblasts, so that the Slit protein or Robo protein of the present invention, an active fragment thereof, or a gene encoding the same can be used as an effective ingredient of a pharmaceutical composition for preventing and treating sarcopenia, and thus is effective.

DESCRIPTION OF DRAWINGS

FIGS. 1A to 1E illustrate changes in body weight and sarcopenic indices in Slit3-deficient male mouse model groups.

FIGS. 2A to 2E illustrate changes in body weight and sarcopenic indices in Slit3-deficient female mouse model groups.

FIGS. 3A to 3D illustrate H&E staining results of EDL muscles of Slit3-deficient male mouse model groups.

FIGS. 4A to 4D illustrate H&E staining results of GC muscles of Slit3-deficient male mouse model groups.

FIGS. 5A to 5D illustrate immunohistochemical staining results of GC muscles of Slit3-deficient male mouse model groups.

FIG. 6 illustrates the confirmation of changes in cell viability of a C2C12 cell line according to Slit3 treatment in order to confirm the effects of Slit3 on promotion of the differentiation of myoblasts.

FIGS. 7A to 7E illustrate a differentiation-increasing effect of Slit3 in the differentiation from myoblasts into myotubes.

FIGS. 8A to 8F illustrate the changes in mRNA expression levels of various myogenic regulatory factors according to Slit3 treatment in the differentiation process of myoblasts.

FIGS. 9A and 9B illustrate changes in protein expression levels of myogenin according to Slit3 treatment in the differentiation process of myoblasts.

FIG. 10 illustrates the difference in number of myogenin positive cells according to Slit3 treatment in the differentiation process of myoblasts.

FIG. 11 is a set of views confirming the types and expression levels of cadherin proteins expressed in myoblasts:

FIG. 11A illustrates mRNA expression levels of M-cadherin and N-cadherin in myoblasts; and

FIG. 11B illustrates protein expression levels of M-cadherin and N-cadherin in myoblasts.

FIG. 12 is a set of views confirming a myoblast differentiation-inducing effect of Slit3 by β-catenin activation.

FIG. 12A illustrates confirmation of β-catenin activity according to the addition of Slit3 in myoblasts;

FIG. 12B illustrates a result of confirming the changes in binding levels of M-cadherin and β-catenin according to Slit3 treatment by co-immunoprecipitation;

FIGS. 12C to 12E illustrate confirmation of myoblast differentiation yield of Slit3 according to the expression inhibition of β-catenin; and

FIG. 12F illustrates changes in expression levels of myogenin in myoblasts treated with Slit3 according to the expression inhibition of β-catenin.

FIG. 13 is a set of views confirming a Robo receptor subtype binding to Slit3 in myoblasts:

FIG. 13A illustrates subtypes of Robo receptors expressed in C2C12 cells which are myoblasts; and

FIGS. 13B to 13D illustrate that a myogenin expression-increasing effect of Slit3 is not significantly increased according to Robo1 or Robo2 knockout in C2C12 cells.

FIGS. 14A to 14E illustrate confirmation of changes in body weight and sarcopenic indices in Robo receptor-deficient mouse models.

FIGS. 15A to 15D illustrate a myoblast differentiation effect of LRRD2 of Slit3 at the in vitro level.

FIGS. 16A to 16E illustrate confirmation of effects of changes in body weight and increases in sarcopenic indices of Slit3 by LRRD2 at the in vivo level.

MODES OF THE INVENTION

As described above, as the average life expectancy is globally increasing, the aging population is increasing, and accordingly, it is expected that the demand for treatment of sarcopenia will also be continuously increased, but no medicine at a level approved by the FDA as a therapeutic agent against sarcopenia has been reported yet.

In a specific embodiment of the present invention, it was confirmed that the Slit protein or the active fragment thereof can bind to a Robo1 or Robo2 receptor to release the β-catenin binding to the M-cadherin of myoblasts via the Slit-Robo system, and thus could promote the formation of muscles by activating the bound β-catenin and increasing the expression of myogenin to induce the differentiation of myoblasts, thereby directly exhibiting effects of treatment against sarcopenia.

Accordingly, the present invention provides a pharmaceutical composition for preventing and alleviating a muscle disease, including one protein selected from the group consisting of Slit1, Slit2, and Slit3 proteins, a Robo1 protein, a Robo2 protein, and a LRRD2 protein, or a gene encoding the same; or an activator thereof, as an effective ingredient.

It is preferred that the “Slit3 protein” of the present invention consists of an amino acid of SEQ ID No. 1, the “Robo1 protein” of the present invention consists of an amino acid of SEQ ID No. 2, the “Robo2 protein” of the present invention consists of an amino acid of SEQ ID No. 3, and the “LRRD2 protein” of the present invention consists of an amino acid of SEQ ID No. 4, and it is possible to include a functional equivalent of the protein or peptide.

The “functional equivalent” has a sequence homology of at least 70% or more, preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more with the amino acid sequences of SEQ ID Nos. 1 to 4 by the addition, substitution, or deletion of amino acids of a protein or peptide, and refers to a protein or peptide exhibiting physiological activity substantially equivalent to that of a protein or peptide consisting of amino acid sequences of SEQ ID Nos. 1 to 4.

The “activator” of the present invention includes various compounds, proteins or peptides, base sequences, and the like capable of enhancing the expression of Slit1, Slit2, Slit3, Robo1, Robo2, and/or fragments thereof or activating an SLIT-ROBO system. Various metabolites, precursors, and pharmaceutical equivalents of the compound, the protein or peptide, and the base sequence are also included in the activator.

In the present invention, the “Slit3 protein” is preferably expressed from a slit3 gene consisting of a base sequence of SEQ ID No. 5, the “Robo1 protein” is preferably expressed from a robo1 gene consisting of a base sequence of SEQ ID No. 6, the “Robo2 protein” is preferably expressed from a robo2 gene consisting of a base sequence of SEQ ID No. 7, and the “LRRD2 protein” is preferably expressed from a gene consisting of a base sequence of SEQ ID No. 8, but are not limited thereto.

It is preferred that the muscle disease of the present invention is a muscle disease caused by muscular function deterioration, muscle wasting, or muscle degeneration and is a disease reported in the art, and specifically, it is more preferred that the muscle disease of the present invention is one or more selected from the group consisting of atony, muscular atrophy, muscular dystrophy, muscle degeneration, myasthenia, cachexia, and sarcopenia, but the muscle disease is not limited thereto.

The muscle wasting or degeneration occurs due to reasons such as congenital factors, acquired factors, and aging, and the muscle wasting is characterized by a gradual loss of muscle mass, and weakening and degeneration of a muscle, particularly, a skeletal muscle or a voluntary muscle and a cardiac muscle.

More specifically, the muscle comprehensively refers to a sinew, a muscle, and a tendon, and the muscular function or muscle function means an ability to exert a force by contraction of the muscle, and includes: muscular strength in which the muscle can exert the maximum contraction force in order to overcome resistance; muscular endurance strength which is an ability to exhibit how long or how many times the muscle can repeat the contraction and relaxation at a given weight; and explosiveness which is an ability to exert a strong force within a short period of time. The muscular function is proportional to muscle mass, and the term “improvement of muscular function” refers to the improvement of the muscular function in a more positive direction.

In preferred embodiments of the present invention, as a result of confirming the relationship between the expression of Slit3 and muscle mass, the present inventors confirmed that in Slit3-deficient mice, the skeletal muscle was decreased (FIG. 1, FIG. 2, and Tables 1 and 2), and the area of the muscle fiber was remarkably decreased, but the numbers of myoblasts and satellite cells thereof were not changed (FIGS. 3 to 5).

Further, as a result of confirming the myoblast differentiation-promoting effect of Slit3, the present inventors confirmed that Slit3 did not affect the viability of myoblasts and enabled myoblasts to be differentiated into myotubes (FIGS. 6 and 7), and confirmed that the expression of myogenin was increased by Slit3 among myogenic regulatory factors participating in the differentiation (FIGS. 8 to 10).

In addition, the present inventors confirmed that in the process in which myoblasts were differentiated into myotubes, the expression of M-cadherin expressed in myoblasts was more abundant than that of N-cadherin, and β-catenin binding to M-cadherin was released, and as a result, the activity of β-catenin was increased by Slit3 (FIGS. 11A, 11B, and 12B), and confirmed that in the differentiation process of myoblasts, the activity of Mβ-catenin could be increased via Slit3, and the expression of myogenin could be increased, thereby participating in the promotion of the formation of muscles by inducing the differentiation of myoblasts (FIGS. 12B, 12C to 12E, and 12F).

Further, as a result of confirming the Robo receptor subtype binding to Slit3 in myoblasts, the present inventors confirmed that Robo1 and Robo2 receptors were expressed on the surface of the myoblast, and as a result, the Robo1 and Robo2 receptors form a Slit-Robo system to exhibit the effects of Slit3 (FIGS. 13A, 13B, and 13C). In particular, since the case where Robo1 is deficient shows that muscle mass is decreased at the in vivo level, the present inventors confirmed that the effects of alleviating sarcopenia could be exhibited via a binding system of Slit3 and Robo1 or Robo2 (Table 3 and FIG. 14).

In addition, as a result of confirming the effects of Slit3 on myoblast differentiation and an increase in muscle mass by a LRRD2 domain, the present inventors confirmed that the effects of Slit3 on the differentiation of myoblasts by LRRD2 were increased at the in vitro level, and the body weight and sarcopenic indices of Slit3 were increased at the in vivo level in the sarcopenic model mice to which LRRD2 was administered (FIGS. 15 and 16 and Table 4).

Accordingly, the Slit protein of the present invention binds to a Robo1 or Robo2 receptor, and as a result, the β-catenin binding to the M-cadherin of myoblasts was released via the Slit-Robo system to activate the β-catenin and increase the expression of myogenin, and subsequently, the formation of muscles can be promoted by inducing the differentiation of myoblasts. Furthermore, not only in the case of treatment of a full-length Slit protein, but also when an active fragment thereof is treated, an increase in muscle mass can be induced by promoting the differentiation of myoblasts, so that particularly preferably, the Slit protein or the LRRD2 protein of Slit3 of the present invention, or a gene encoding the same can be used as an effective ingredient of a pharmaceutical composition for preventing and treating sarcopenia.

For the protein or peptide of the present invention, not only a protein or peptide having a wild-type amino acid sequence thereof, but also an amino acid sequence variant thereof may also be included in the scope of the present invention. The amino acid sequence variant refers to a protein or peptide in which a wild-type amino acid sequence of Slit1, Slit2, Slit3, Robo1, Robo2, or LRRD2 has a different sequence by deletion, insertion, non-conservative or conservative substitution of one or more amino acid residues, or a combination thereof.

Amino acid exchanges possible in proteins and peptides that do not wholly change the activities of the molecules are known in the art (H. Neurath, R. L. Hill, The Proteins, Academic Press, New York, 1979). The most typically occurring exchanges are exchanges between amino acid residues Ala/Ser, Val/Ile, Asp/Glu, Thr/Ser, Ala/Gly, Ala/Thr, Ser/Asn, Ala/Val, Ser/Gly, Thy/Phe, Ala/Pro, Lys/Arg, Asp/Asn, Leu/Ile, Leu/Val, Ala/Glu, and Asp/Gly. In some cases, amino acids may also be modified by phosphorylation, sulfation, acetylation, glycosylation, methylation, farnesylation, or the like.

The Slit1, Slit2, Slit3, Robo1, Robo2 proteins and the LRRD2 protein of the present invention, or variants thereof can be extracted from nature or synthesized (Merrifield, J. Amer. Chem. Soc. 85:2149-2156, 1963) or prepared by a gene recombinant method based on a DNA sequence (Sambrook et al., Molecular Cloning, Cold Spring Harbour Laboratory Press, New York, USA, 2d Ed., 1989).

The Slit1, Slit2, Slit3, Robo1, Robo2 proteins and the LRRD2 protein may be provided in the form of a protein or in the form of an expression vector capable of expressing a gene encoding Slit3, Robo1, Robo2 proteins, and the LRRD2 protein in the cells in order to be used for gene therapy or a vaccine, and the like.

As the expression vector, it is possible to use an expression vector capable of inserting a gene encoding the Slit1, Slit2, Slit3, Robo1, Robo2 proteins or the LRRD2 protein and expressing the protein, and for example, it is possible to use an expression vector such as pBK-CMV (Stratagene) or pCR3.1 (Invitrogen).

Further, a polynucleotide can be administered in a form in which a base sequence encoding the Slit1, Slit2, Slit3, Robo1, Robo2 proteins and the LRRD2 protein of the present invention, that is, a recombinant DNA molecule including the polynucleotide is operably linked to a nucleic acid sequence regulating expression, for example, in the form of an expression vector, such that the base sequence is expressed in a patient to be treated. It is preferred that the vector accordingly includes a suitable transcription regulatory signal including a promoter site capable of expressing a coding sequence, and the promoter being operable in a patient to be treated. Accordingly, for human gene therapy, the term “promoter” including not only a sequence required to deliver a RNA polymerase to a transcription initiation site, but also other operative sequences or regulatory sequences including an enhancer, if appropriate may be preferably a human promoter sequence from a human gene or generally a human promoter sequence from a gene expressed in a human, for example, a promoter from a human cytomegalovirus (CMV). From this viewpoint, among suitable known eukaryotic promoters, the CMVs, that is, a retrovirus LTR promoter such as an early promoter, a HSV thymidine kinase promoter, an early and late SV40 promoter, and promoters of a Rous sarcoma virus (“RSV”), and a metallothionein promoter such as a mouse metallothionein-1 promoter are suitable.

The polynucleotide sequence and the transcription regulatory sequence may be provided and cloned into a replicable plasmid vector, based on commercially available plasmids such as pBR322, or may also be constructed from available plasmids by the routine application of well-known published procedures.

The vector may also include a transcriptional regulatory sequence, located at 3′ of the gene sequence, and a polyadenylation sequence, recognizable in a patient to be treated, such as the corresponding sequence from a virus such as the SV40 virus, when used for human therapy. Other transcription regulatory sequences are well known in the art, and thus can be used.

The expression vector may also include a selectable marker, such as antibiotic resistance, which enables the vector to be propagated.

Expression vectors capable of in situ synthesizing the protein or peptide may be introduced into a wound site directly by physical methods. Examples of these methods include topical application of a “naked” nucleic acid vector in a suitable vehicle, for example, in a solution in a pharmaceutically acceptable excipient such as phosphate buffered saline (PBS), or administration of a vector by physical methods such as particle bombardment, also known as “gene gun” technology, according to methods known in the art. As described in U.S. Pat. No. 5,371,015, the “gene gun” technology is a method in which inert particles, such as gold beads coated with a vector are accelerated at a speed sufficient to enable the particles to penetrate a wound site, for example, the surface of skin cells, by means of discharge under high pressure from a propelling device. In addition, other physical methods of administering DNA directly to a receptor include ultrasound, electrical stimulation, electroporation, microseeding, and the like.

The gene sequence may also be administered to the wound site by means of transformed host cells. Such cells include cells harvested from a patient, and the nucleic acid sequence may be introduced into the cells by gene transfer methods known in the art, followed by growth of the transformed cells in a culture solution and transplantation into the patient.

The expression construct as described above may be used in the treatment of the present invention by various methods. Accordingly, the expression constructs may be directly administered to a site of a patient to be treated.

Furthermore, the pharmaceutical composition of the present invention may include an activation factor for increasing the expression of the Slit1, Slit2, Slit3, Robo1, Robo2 protein or the LRRD2 protein as an effective ingredient.

The activation factor for increasing the expression of the Slit1, Slit2, Slit3, Robo1, Robo2 protein or the LRRD2 protein refers to a material that directly or indirectly acts on the slit1, slit2, slit3, robo1, robo2 gene or a gene encoding LRRD2 to improve, induce, stimulate, and increase the biological activity of the Slit1, Slit2, Slit3, Robo1, Robo2 protein or the LRRD2 protein. The material includes a single compound such as an organic or inorganic compound, a biopolymer compound such as a peptide, a protein, a nucleic acid, a carbohydrate, and a lipid, a complex of multiple compounds, and the like. The activation factor for increasing the expression of slit1, slit2, or slit3 may be used in prevention, alleviation, and treatment of a disease occurring due to a decrease in expression, activity, or function of slit1, slit2, or slit3.

A mechanism whereby the material activates the slit1, slit2, slit3, robo1, robo2 gene or a gene encoding LRRD2 is not particularly limited. For example, the material may increase the expression of a gene, such as transcription and translation, or may function as a mechanism that converts a non-active type into an active type. Preferably, the material activating the slit1, slit2, slit3, robo1, robo2 gene or a gene encoding LRRD2 is a biopolymer compound such as a peptide, a protein, a nucleic acid, a carbohydrate, and a lipid. With respect to the slit1, slit2, and slit3, nucleic acid and protein sequences of which are already known, a single compound peptide such as an organic or inorganic compound which acts as an inducer or an activator, a biopolymer compound such as a peptide, a protein, a nucleic acid, a carbohydrate, and a lipid, a complex of multiple compounds, and the like may be prepared or screened by using technologies known in the art.

The composition of the present invention may be in the form of various oral or parenteral formulations. When the composition is formulated, the composition may be prepared by using a buffer (for example, a saline solution or PBS), an antioxidant, a bacteriostatic agent, a chelating agent (for example, EDTA or glutathione), a filler, an extender, a binder, an adjuvant (for example, aluminum hydroxide), a suspension agent, a thickener, a wetting agent, a disintegrant, or a surfactant, a diluent or an excipient.

Examples of a solid preparation for oral administration include a tablet, a pill, a powder, a granule, a capsule, and the like, and the solid preparation is prepared by mixing one or more compounds with one or more excipients, for example, starch (including corn starch, wheat starch, rice starch, potato starch, and the like), calcium carbonate, sucrose, lactose, dextrose, sorbitol, mannitol, xylitol, erythritol, maltitol, cellulose, methyl cellulose, sodium carboxymethylcellulose and hydroxypropymethyl-cellulose, gelatin, or the like. For example, a tablet or a sugar tablet may be obtained by blending an active ingredient with a solid excipient, pulverizing the resulting blend, adding a suitable auxiliary agent thereto, and then processing the resulting mixture into a granular mixture.

Further, in addition to a simple excipient, lubricants such as magnesium stearate and talc are also used. A liquid preparation for oral administration corresponds to a suspension agent, a liquid for internal use, an emulsion, a syrup, and the like, and the liquid preparation may include, in addition to water and liquid paraffin which are simple commonly used diluents, various excipients, for example, a wetting agent, a sweetener, an odorant, a preservative, and the like. In addition, in some cases, cross-linked polyvinyl pyrrolidone, agar, alginic acid, sodium alginate, or the like as a disintegrant may be added, and an anti-coagulant, a lubricant, a wetting agent, a fragrance, an emulsifier, an antiseptic, and the like may be additionally added.

Examples of a preparation for parenteral administration include an aqueous sterile solution, a non-aqueous solvent, a suspension solvent, an emulsion, a freeze-dried preparation, a suppository, or the like. As the non-aqueous solvent and the suspension solvent, it is possible to use propylene glycol, polyethylene glycol, a vegetable oil such as olive oil, an injectable ester such as ethyl oleate, and the like. As a base of the suppository, it is possible to use Witepsol, Macrogol, Tween 61, cacao butter, laurin fat, glycerol, gelatin, and the like.

The composition of the present invention may be administered orally or parenterally, and, when administered parenterally, may be formulated in the form of a preparation for external application to the skin; an injection administered intraperitoneally, rectally, intravenously, muscularly, subcutaneously, or intracerebroventricularly, or via cervical intrathecal injection; a percutaneous administration agent; or a nasal inhaler according to a method known in the art.

The injection must be sterilized and protected from contamination of microorganisms such as bacteria and fungi. Examples of a suitable carrier for the injection may be, but are not limited to, a solvent or a dispersion medium including water, ethanol, polyols (for example, glycerol, propylene glycol, liquid polyethylene glycol, and the like), mixtures thereof, and/or vegetable oils. More preferably, as a suitable carrier, it is possible to use an isotonic solution such as Hank's solution, Ringer's solution, triethanolamine-containing phosphate buffered saline (PBS) or sterile water for injection, 10% ethanol, 40% propylene glycol, and 5% dextrose, and the like. To protect the injection from microorganism contamination, various antimicrobial agents and antifungal agents such as paraben, chlorobutanol, phenol, sorbic acid, and thimerosal may be additionally included. Furthermore, in most cases, the injection may additionally include an isotonic agent such as sugar or sodium chloride.

Examples of the percutaneous administration agent include a form such as an ointment, a cream, a lotion, a gel, a solution for external use, a paste, a liniment, and an aerosol. The percutaneous administration as described above means that an effective amount of an active ingredient contained in a pharmaceutical composition is delivered into the skin via local administration thereof to the skin.

In the case of a preparation for inhalation, the compound used according to the present invention may be conveniently delivered in the form of an aerosol spray from a pressurized pack or a nebulizer by using a suitable propellant, for example, dichlorofluoromethane, trichlorofluoromethane, dichlorotetrafluoroethane, carbon dioxide, or other suitable gases. In the case of the pressurized aerosol, a dosage unit may be determined by providing a valve for transferring a weighed amount. For example, a gelatin capsule and a cartridge for use in an inhaler or insufflator may be formulated so as to contain a powder mixture of a compound and a suitable powder base such as lactose or starch. Formulations for parenteral administration are described in the document, which is a guidebook generally known in all pharmaceutical chemistry fields (Remington's Pharmaceutical Science, 15th Edition, 1975. Mack Publishing Company, Easton, Pa. 18042, Chapter 87: Blaug, Seymour).

The composition of the present invention is administered in a pharmaceutically effective amount. The term “pharmaceutically effective amount” as used herein refers to an amount sufficient to treat diseases at a reasonable benefit/risk ratio applicable to medical treatment, and an effective dosage level may be determined according to factors including type of diseases of patients, the severity of disease, the activity of drugs, sensitivity to drugs, administration time, administration routes, excretion rate, treatment periods, and simultaneously used drugs, and factors well known in other medical fields. The composition according to the present invention may be administered as an individual therapeutic agent or in combination with other therapeutic agents, may be administered sequentially or simultaneously with therapeutic agents in the related art, and may be administered in a single dose or multiple doses. That is, the total effective amount of the composition of the present invention may be administered to a patient in a single dose or may be administered by a fractionated treatment protocol, in which multiple doses are administered over a long period of time. It is important to administer the composition in a minimum amount that can obtain the maximum effect without any side effects, in consideration of all the aforementioned factors, and this may be easily determined by the person skilled in the art.

A dosage of the pharmaceutical composition of the present invention varies according to body weight, age, gender, and health status of a patient, diet, administration time, administration method, excretion rate, and the severity of a disease. A daily dosage thereof may be administered parenterally in an amount of preferably 0.01 mg to 50 mg, and more preferably 0.1 mg to 30 mg per kg of body weight a day based on the Slit1, Slit2, Slit3, Robo1, Robo2 protein or the LRRD2 protein, and a daily dosage thereof may be administered orally in a single dose or multiple doses in an amount of preferably 0.01 mg to 100 mg, and more preferably 0.01 mg to 10 mg per kg of body weight a day based on the Slit1, Slit2, Slit3, Robo1, Robo2 protein or the LRRD2 protein. However, since the dosage may be increased or decreased depending on the administration route, the severity of obesity, the gender, the body weight, the age, and the like, the dosage is not intended to limit the scope of the present invention in any way.

The composition of the present invention may be used either alone or in combination with surgery, radiation therapy, hormone therapy, chemotherapy, and methods using a biological response modifier.

The pharmaceutical composition of the present invention may also be provided in the form of a formulation for external use, including the Slit1, Slit2, Slit3, Robo1, Robo2 protein or the LRRD2 protein, or a base sequence encoding the same as an effective ingredient. When the pharmaceutical composition for preventing and treating a muscle disease according to the present invention is used as a preparation for external application to the skin, the pharmaceutical composition may additionally contain auxiliary agents typically used in the dermatology field, such as any other ingredients typically used in the preparation for external application to the skin, such as a fatty substance, an organic solvent, a solubilizing agent, a thickener and a gelling agent, a softener, an antioxidant, a suspending agent, a stabilizer, a foaming agent, an odorant, a surfactant, water, an ionic emulsifier, a non-ionic emulsifier, a filler, a metal ion blocking agent, a chelating agent, a preservative, a vitamin, a blocking agent, a wetting agent, an essential oil, a dye, a pigment, a hydrophilic active agent, a lipophilic active agent, or a lipid vesicle. In addition, the ingredients may be introduced in an amount generally used in the dermatology field.

When the pharmaceutical composition for preventing and treating a muscle disease according to the present invention is provided as a preparation for external application to the skin, the pharmaceutical composition may be in the form of a formulation such as an ointment, a patch, a gel, a cream, and an aerosol, but is not limited thereto.

Furthermore, the present invention provides a health functional food for preventing and alleviating a muscle disease, including one protein selected from the group consisting of a Slit1 protein, a Slit2 protein, a Slit3 protein, a Robo1 protein, a Robo2 protein, and a LRRD2 protein, or a gene encoding the same, as an effective ingredient.

It is preferred that the “Slit3 protein” of the present invention consists of an amino acid of SEQ ID No. 1, the “Robo1 protein” of the present invention consists of an amino acid of SEQ ID No. 2, the “Robo2 protein” of the present invention consists of an amino acid of SEQ ID No. 3, and the “LRRD2 protein” of the present invention consists of an amino acid of SEQ ID No. 4, and it is possible to include a functional equivalent of the protein or peptide.

The “functional equivalent” has a sequence homology of at least 70% or more, preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more with the amino acid sequences of SEQ ID Nos. 1 to 4 by the addition, substitution, or deletion of amino acids of a protein or peptide, and refers to a protein or peptide exhibiting physiological activity substantially equivalent to that of a protein or peptide consisting of amino acid sequences of SEQ ID Nos. 1 to 4.

In the present invention, the “Slit3 protein” is preferably expressed from a slit3 gene consisting of a base sequence of SEQ ID No. 5, the “Robo1 protein” is preferably expressed from a robo1 gene consisting of a base sequence of SEQ ID No. 6, the “Robo2 protein” is preferably expressed from a robo2 gene consisting of a base sequence of SEQ ID No. 7, and the “LRRD2 protein” is preferably expressed from a gene consisting of a base sequence of SEQ ID No. 8, but are not limited thereto.

It is preferred that the muscle disease of the present invention is a muscle disease caused by muscular function deterioration, muscle wasting, or muscle degeneration and is a disease reported in the art, and specifically, it is more preferred that the muscle disease of the present invention is one or more selected from the group consisting of atony, muscular atrophy, muscular dystrophy, muscle degeneration, myasthenia, cachexia, and sarcopenia, but the muscle disease is not limited thereto.

The muscle wasting or degeneration occurs for reasons such as congenital factors, acquired factors, and aging, and the muscle wasting is characterized by a gradual loss of muscle mass, and weakening and degeneration of a muscle, particularly, a skeletal muscle or a voluntary muscle and a cardiac muscle.

More specifically, the muscle comprehensively refers to a sinew, a muscle, and a tendon, and the muscular function or muscle function means an ability to exert a force by contraction of the muscle, and includes: muscular strength in which the muscle can exert the maximum contraction force in order to overcome resistance; muscular endurance strength which is an ability to exhibit how long or how many times the muscle can repeat the contraction and relaxation at a given weight; and explosiveness which is an ability to exert a strong force within a short period of time. The muscular function is proportional to muscle mass, and the term “improvement of muscular function” refers to the improvement of the muscular function in a more positive direction.

The Slit protein of the present invention binds to a Robo1 or Robo2 receptor, and as a result, the β-catenin binding to the M-cadherin of myoblasts was released via the Slit-Robo system to activate the β-catenin and increase the expression of myogenin, and subsequently, the formation of muscles can be promoted by inducing the differentiation of myoblasts. Further, not only in the case of treatment of a full-length Slit protein, but also when an active fragment thereof, particularly preferably, a LRRD2 protein is treated, an increase in muscle mass can be induced by promoting the differentiation of myoblasts, so that the Slit protein of the present invention or an active fragment of Slit, or a gene encoding the same can be used as an effective ingredient of a health functional food for preventing and alleviating sarcopenia. Further, the Slit protein of the present invention or an active fragment of Slit, or a gene encoding the same can be used as an effective ingredient of a feed composition for preventing and alleviating sarcopenia.

The food composition according to the present invention can be prepared in various forms by typical methods known in the art. A general food can be prepared by adding the Slit1, Slit2, Slit3, Robo1, Robo2 protein or the LRRD2 protein of the present invention to, without being limited to, a beverage (including an alcoholic beverage), fruit and a processed food thereof (for example: canned fruit, bottled food, jam, marmalade, and the like), fish, meat and processed food thereof (for example: ham, sausage, corned beef, and the like), bread and noodles (for example: thick wheat noodles, buckwheat noodles, instant noodles, spaghetti, macaroni, and the like), fruit juices, various drinks, cookies, wheat-gluten, dairy products (for example: butter, cheese, and the like), edible vegetable oils, margarine, vegetable protein, retort foods, frozen food and various seasonings (for example: soybean paste, soy sauce, sauce, and the like), and the like. In addition, a nutrition supplement can be prepared by adding the Slit1, Slit2, Slit3, Robo1, Robo2 protein or the LRRD2 protein of the present invention to, without being limited to, a capsule, a tablet, a pill, and the like. Furthermore, for a health functional food, for example, the Slit1, Slit2, Slit3, Robo1, Robo2 protein or the LRRD2 protein of the present invention itself is prepared in the form of, without being limited to, tea, juice, and drink and can be taken by being processed into a liquid, a granule, a capsule, and a powder so as to be able to be drunk (health beverage). Further, the Slit1, Slit2, Slit3, Robo1, Robo2 protein or the LRRD2 protein of the present invention can be used and prepared in the form of a powder or a concentrated liquid so as to be used in the form of a food additive. In addition, the food composition of the present invention can be prepared in the form of a composition by mixing the Slit1, Slit2, Slit3, Robo1, Robo2 protein or the LRRD2 protein of the present invention with a known active ingredient known to have effects of preventing a muscle disease and improving muscular function.

When the Slit1, Slit2, Slit3, Robo1, Robo2 protein or the LRRD2 protein of the present invention is used as a health beverage, the health beverage composition can contain various flavoring agents or natural carbohydrates, and the like as additional ingredients, such as a typical beverage. The above-described natural carbohydrates may be monosaccharides such as glucose and fructose; disaccharides such as maltose and sucrose; polysaccharides such as dextrin and cyclodextrin; and sugar alcohols such as xylitol, sorbitol, and erythritol. As a sweetener, it is possible to use a natural sweetener such as thaumatin and a stevia extract; a synthetic sweetener such as saccharin and aspartame, and the like. The proportion of the natural carbohydrate is generally about 0.01 to 0.04 g, and preferably about 0.02 to 0.03 g per 100 mL of the composition of the present invention.

Furthermore, the Slit1, Slit2, Slit3, Robo1, Robo2 protein or the LRRD2 protein of the present invention may be contained as an effective ingredient of a food composition for preventing a muscle disease and improving muscular function, and the amount thereof is an amount effective to achieve an action for preventing a muscle disease and improving muscular function and is not particularly limited, but is preferably 0.01 to 100 wt % based on the total weight of the entire composition. Further, the food composition according of the present invention can be prepared by mixing the Slit1, Slit2, Slit3, Robo1, Robo2 protein or the LRRD2 protein with other active ingredients known to have effects of preventing a muscle disease and improving muscular function.

In addition to the aforementioned ingredients, the health food of the present invention may contain various nutrients, vitamins, electrolytes, flavoring agents, coloring agents, pectic acid, salts of pectic acid, alginic acid, salts of alginic acid, organic acids, protective colloidal thickeners, pH adjusting agents, stabilizers, preservatives, glycerin, alcohols, carbonating agents, and the like. Besides, the health food of the present invention may contain the flesh for preparing natural fruit juice, fruit juice beverage, or vegetable beverage. These ingredients may be used either alone or in mixtures thereof. The proportion of these additives is not significantly important, but is generally selected within a range of 0.01 to 0.1 part by weight per 100 parts by weight of the composition of the present invention.

In addition, the present invention provides a cosmetic composition for improving muscular function, including one protein selected from the group consisting of a Slit1 protein, a Slit2 protein, a Slit3 protein, a Robo1 protein, a Robo2 protein, and a LRRD2 protein, or a gene encoding the same, as an effective ingredient. The cosmetic composition is not particularly limited, but may be used for external application to the skin, or orally ingested.

It is preferred that the “Slit3 protein” of the present invention consists of an amino acid of SEQ ID No. 1, the “Robo1 protein” of the present invention consists of an amino acid of SEQ ID No. 2, the “Robo2 protein” of the present invention consists of an amino acid of SEQ ID No. 3, and the “LRRD2 protein” of the present invention consists of an amino acid of SEQ ID No. 4, and it is possible to include a functional equivalent of the protein or peptide.

The “functional equivalent” has a sequence homology of at least 70% or more, preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more with the amino acid sequences of SEQ ID Nos. 1 to 4 by the addition, substitution, or deletion of amino acids of a protein or peptide, and refers to a protein or peptide exhibiting physiological activity substantially equivalent to that of a protein or peptide consisting of amino acid sequences of SEQ ID Nos. 1 to 4.

In the present invention, the “Slit3 protein” is preferably expressed from a slit3 gene consisting of a base sequence of SEQ ID No. 5, the “Robo1 protein” is preferably expressed from a robo1 gene consisting of a base sequence of SEQ ID No. 6, the “Robo2 protein” is preferably expressed from a robo2 gene consisting of a base sequence of SEQ ID No. 7, and the “LRRD2 protein” is preferably expressed from a gene consisting of a base sequence of SEQ ID No. 8, but are not limited thereto.

It is preferred that the muscle disease of the present invention is a muscle disease caused by muscular function deterioration, muscle wasting, or muscle degeneration and is a disease reported in the art, and specifically, it is more preferred that the muscle disease of the present invention is one or more selected from the group consisting of atony, muscular atrophy, muscular dystrophy, muscle degeneration, myasthenia, cachexia, and sarcopenia, but the muscle disease is not limited thereto.

The muscle wasting or degeneration occurs for reasons such as congenital factors, acquired factors, and aging, and the muscle wasting is characterized by a gradual loss of muscle mass, and weakening and degeneration of a muscle, particularly, a skeletal muscle or a voluntary muscle and a cardiac muscle.

More specifically, the muscle comprehensively refers to a sinew, a muscle, and a tendon, and the muscular function or muscle function means an ability to exert a force by contraction of the muscle, and includes: muscular strength in which the muscle can exert the maximum contraction force in order to overcome resistance; muscular endurance strength which is an ability to exhibit how long or how many times the muscle can repeat the contraction and relaxation at a given weight; and explosiveness which is an ability to exert a strong force within a short period of time. The muscular function is proportional to muscle mass, and the term “improvement of muscular function” refers to the improvement of the muscular function in a more positive direction.

The Slit protein of the present invention binds to a Robo1 or Robo2 receptor, and as a result, the β-catenin binding to the M-cadherin of myoblasts was released via the Slit-Robo system to activate the β-catenin and increase the expression of myogenin, and subsequently, the formation of muscles can be promoted by inducing the differentiation of myoblasts. Furthermore, not only in the treatment of a full-length Slit protein, but also when an active fragment thereof, particularly preferably, a LRRD2 protein is treated, an increase in muscle mass can be induced by promoting the differentiation of myoblasts, so that the Slit protein of the present invention or an active fragment of Slit, or a gene encoding the same can be used as an effective ingredient of a cosmetic composition for improving muscular function.

The composition for improving muscular function of the present invention may also be a cosmetic composition. The cosmetic composition of the present invention contains a Slit1 protein, a Slit2 protein, a Slit3 protein, a Robo1 protein, a Robo2 protein or a LRRD2 protein as an effective ingredient, and may be prepared in the form of a basic cosmetic composition (a lotion, a cream, an essence, a cleanser such as cleansing foam and cleansing water, a pack, and a body oil), a coloring cosmetic composition (a foundation, a lip-stick, a mascara, and a make-up base), a hair product composition (a shampoo, a rinse, a hair conditioner, and a hair gel), a soap, and the like with dermatologically acceptable excipients.

The excipient may include, for example, but not limited thereto, a skin softener, a skin infiltration enhancer, a coloring agent, an aroma, an emulsifier, a thickener, and a solvent. Further, it is possible to additionally include a fragrance, a pigment, a disinfectant, an antioxidant, a preservative, a moisturizer and the like, and to include a thickening agent, inorganic salts, a synthetic polymer material, and the like for improving physical properties. For example, when a cleanser and a soap are prepared by using the cosmetic composition of the present invention, the cleanser and the soap may be easily prepared by adding the Slit1 protein, Slit2 protein, Slit3 protein, Robo1 protein, Robo2 protein, or LRRD2 protein to a typical cleanser and soap base. When a cream is prepared, the cream may be prepared by adding the Slit1 protein, Slit2 protein, Slit3 protein, Robo1 protein, Robo2 protein, or LRRD2 protein, or a base sequence encoding the same to a general oil-in-water (O/W) cream base. It is possible to further add a fragrance, a chelating agent, a pigment, an antioxidant, a preservative, and the like, and synthetic or natural materials such as proteins, minerals or vitamins for the purpose of improving physical properties.

The content of the Slit1 protein, Slit2 protein, Slit3 protein, Robo1 protein, Robo2 protein or the LRRD2 protein contained in the cosmetic composition of the present invention is, but not limited to, preferably 0.001 to 10 wt %, and more preferably 0.01 to 5 wt %, based on the total weight of the entire composition. When the content is less than 0.001 wt %, desired anti-aging or wrinkle-reducing effects cannot be expected, and when the content exceeds 10 wt %, it may be difficult to prepare the cosmetic composition of the present invention for reasons such as safety or formulation.

In addition, the present application provides a method for detecting a protein for providing information on diagnosis of a muscle disease, the method including the steps:

i) measuring an expression level of a Slit3 protein consisting of an amino acid sequence of SEQ ID No. 1 from a subject-derived sample which is an experimental group;

ii) comparing the expression level of the Slit3 protein measured in Step i) with an expression level of a Slit3 protein of a normal individual-derived sample which is a control group; and

iii) determining the experimental group as a muscle disease when the expression level of the Slit3 protein of the experimental group compared in Step ii) is decreased as compared to that of the control group.

In the present invention, the “measuring the expression level of the protein” may be confirmed by measuring the expression level of mRNA or the protein.

Furthermore, the present invention provides a method for screening a therapeutic agent against a muscle disease, the method including the steps of:

i) treating a cell line expressing one or more selected from the group consisting of a Slit3 protein consisting of an amino acid sequence of SEQ ID No. 1, a Robo1 protein consisting of an amino acid sequence of SEQ ID No. 2, and a Robo2 protein consisting of an amino acid sequence of SEQ ID No. 3 with a subject compound or composition;

ii) measuring an expression degree of the Slit3 protein or activity of the Robo1 protein or Robo2 protein in the cell line treated in Step i); and

iii) selecting a subject compound or composition in which the expression degree of the Slit3 or the activity of the Robo1 protein or Robo2 protein in Step ii) is increased in comparison with that of the control group cell line which is not treated with the subject compound or composition.

It is preferred that the muscle disease of the present invention is a muscle disease caused by muscular function deterioration, muscle wasting, or muscle degeneration and is a disease reported in the art, and specifically, it is more preferred that the muscle disease of the present invention is one or more selected from the group consisting of atony, muscular atrophy, muscular dystrophy, muscle degeneration, myasthenia, cachexia, and sarcopenia, but the muscle disease is not limited thereto.

The muscle wasting or degeneration occurs for reasons such as congenital factors, acquired factors, and aging, and the muscle wasting is characterized by a gradual loss of muscle mass, and weakening and degeneration of a muscle, particularly, a skeletal muscle or a voluntary muscle and a cardiac muscle.

More specifically, the muscle comprehensively refers to a sinew, a muscle, and a tendon, and the muscular function or muscle function means an ability to exert a force by contraction of the muscle, and includes: muscular strength in which the muscle can exert the maximum contraction force in order to overcome resistance; muscular endurance strength which is an ability to exhibit how long or how many times the muscle can repeat the contraction and relaxation at a given weight; and explosiveness which is an ability to exert a strong force within a short period of time. The muscular function is proportional to muscle mass, and the term “improvement of muscular function” refers to the improvement of the muscular function in a more positive direction.

The Slit protein of the present invention or a LRRD2 protein thereof binds to a Robo1 or Robo2 receptor, and as a result, the β-catenin binding to the M-cadherin of myoblasts was released via the Slit-Robo system to activate the β-catenin and increase the expression of myogenin, and subsequently, the formation of muscles can be promoted by inducing the differentiation of myoblasts. Accordingly, it is possible to determine the onset of sarcopenia before direct symptoms appear through the expression level of the Slit protein or the LRRD2 protein thereof. Further, it is possible to select a compound or composition capable of increasing the expression level of the Slit protein or the activity of the Robo receptor as a candidate material for a therapeutic agent against sarcopenia.

In the method of the present invention, in the measurement of the expression level of mRNA, the amount of mRNA is measured by a process of confirming the presence or absence and expression degree of mRNA encoding the SLIT3 protein or LRRD2 protein in a biological sample. As an analysis method for the same, a method known in the art may be used, and examples thereof include polymerase chain reaction (PCR), reverse transcription-polymerase chain reaction (RT-PCR), competitive RT-PCR, real time RT-PCR, RNase protection assay (RPA), Northern blotting, DNA chips, and the like, but are not limited thereto.

In the method of the present invention, the measurement of the expression level of a protein refers to the measurement of an amount of a protein through a process of confirming the presence or absence and expression degree of the SLIT3 protein or LRRD2 protein in a biological sample. Preferably, the amount of the protein may be confirmed by using an antibody specifically binding to the protein of the gene. As an analysis method for the same, a method known in the art may be used, and examples thereof include enzyme linked immunosorbent assay (ELISA), radioimmunoassay (RIA), an Ouchterlony immunodiffusion method, rocket immunoelectrophoresis, tissue immunostaining, an immunoprecipitation assay, a complement fixation assay, fluorescence activated cell sorter (FACS), a protein chip, and the like, but are not limited thereto.

In the method for detecting a protein for providing information on diagnosis of a muscle disease and the method for screening a therapeutic agent against a muscle disease, the Slit3 in a preferred embodiment is used and described, but Slit1, Slit2; or an active fragment of Slit1, Slit2, and Slit3 may be used.

BEST MODE

Hereinafter, the present invention will be described in more detail through Examples. These Examples are only for exemplifying the present invention, and it will be obvious to a person with ordinary skill in the art that the scope of the present invention is not to be interpreted as being limited by these Examples.

Example 1 Confirmation of Relationship Between Slit3 Expression and Muscle Mass <1-1> Confirmation of Changes in Body Weight and Sarcopenic Indices in Slit3-Deficient Mouse Model

In order to confirm whether Slit3 participated in the formation of skeletal muscles in vivo, a change in muscle mass in a mouse model was confirmed according to the presence or absence of Slit3 expression.

Specifically, embryos of slit3 knockout mice were purchased from Mutant Mouse Regional Resource Centers (Stock number 030759-MU; Columbia, Mo., USA), and a Slit3-deficient mouse model was prepared by breeding the male and female slit3+/−C57BL/6J mice. The Slit3-deficient mouse model was again divided into a male group and a female group to measure the body weight of the mouse model in which the Slit3 expression was deficient. When the mouse model became 7 weeks old, the male group and the female group were sacrificed, and the body weights thereof were measured by obtaining the muscles of each extensor digitorum longus (EDL) and gastrocnemius and soleus (GC+SOL). The sarcopenic index is shown by using the equation “sarcopenic index (%)=100×the weight of the muscle/the body weight” in order to denote muscle mass as a percentage of the body weight of a mouse.

As a result, as shown in FIG. 1, FIG. 2, and the following [Table 1] and [Table 2], it was confirmed that in the Slit3-deficient mouse model, the body weights of the male group and the female group were lower than those of the mice in the normal control group, the weights of the EDL and the weights of the GC+SOL in the male group and the female group were also lower than those in the normal control group, and the sarcopenic indices of the EDL and the sarcopenic indices of the GC+SOL were also significantly decreased as compared to those in the normal control group (FIG. 1, FIG. 2, Table 1, and Table 2). Through this, it was confirmed that when Slit3 was deficient in vivo regardless of gender and type of muscle, skeletal system muscle mass was also decreased.

TABLE 1 Comparison of Changes in Body Weight and Sarcopenic Indices in Slit-Deficient Male Mice Experimental Body Muscle weight (g) Sarcopenic index (%) group weight (g) EDL GC + SOL EDL GC + SOL Normal 22.8 ± 0.058 ± 0.131 ± 0.257 ± 0.578 ± control 0.7 0.002 0.001 0.011 0.015 group Slit3- 19.8 ± 0.041 ± 0.101 ± 0.207 ± 0.507 ± deficient 1.0 0.003 0.008 0.014 0.022 group

TABLE 2 Comparison of Changes in Body Weight and Sarcopenic Indices in Slit-Deficient Female Mice Experimental Body Muscle weight (g) Sarcopenic index (%) group weight (g) EDL GC + SOL EDL GC + SOL Normal 18.6 ± 0.047 ± 0.104 ± 0.250 ± 0.558 ± control 0.5 0.006 0.007 0.026 0.028 group Slit3- 18.2 ± 0.031 ± 0.083 ± 0.171 ± 0.458 ± deficient 0.4 0.003 0.004 0.020 0.028 group

<1-2> Confirmation of Changes in Muscle Area in Slit3-Deficient Mouse Model

Since it was confirmed that the skeletal muscles in the Slit3-deficient mice were decreased, muscle areas were compared by staining the muscles in order to confirm that the muscles were decreased.

Specifically, EDL and GC+SOL muscle tissues were obtained by sacrificing the 7 week-old female mouse model group in which Slit3 was deficient, and then fixed in 4% formaldehyde and embedded in an OCT compound. And then, the muscle tissues were stained through hematoxylin & eosin (H-E) staining by treatment with hematoxylin and eosin. By the stained muscle tissues and using the ImageJ software, the numbers of nuclei and fibrous portions of the muscle tissues were compared and the areas were confirmed.

Further, in order to more specifically compare the numbers of the cells, marker proteins for the sarcolemma, the nucleus, and the satellite cells that are stem cells of myoblasts were immunohistochemically stained. After a reaction was carried out according to the manufacturer's protocol by treating the cross-section of the GC muscle tissue with each of an anti-laminin antibody and an anti-PAX7 antibody as primary antibodies, the marker proteins for the sarcolemma and the satellite cells that are stem cells of myoblasts were stained by developing color with a secondary antibody, the nucleus was stained by treatment with 4′6-diamidino-2-phenylindole (DAPI), and then the proportion of the stem cells of myoblasts in cells in the GC muscle tissues was obtained by observing the GC muscle tissues with a fluorescence microscope.

As a result, as illustrated in FIGS. 3 to 5, it was confirmed that in the Slit3-deficient mouse model, the numbers of muscle fibers and nuclei in the EDL and GC muscles were similar to each other as compared to those in the normal control group mice (FIGS. 3 and 4). It was confirmed that when the cross-section of the GC tissue was immunohistochemically stained, the area of the muscle fibers in the Slit3-deficient mice was significantly decreased through laminin staining, whereas the number of total nuclei and the number of PAX7 positive cells in the tissue did not exhibit any significant difference through staining of the nucleus and PAX7 (FIG. 5). Through this, it was confirmed that when Slit3 was deficient at the in vivo level, the area of the muscle fiber was remarkably decreased, but the numbers of myoblasts and satellite cells thereof were not changed, and accordingly, the decrease in muscle mass caused by Slit3 deficiency is independent of the proliferation of myoblasts and the proliferation and recruitment of satellite cells thereof.

Example 2 Confirmation of Myoblast Differentiation-Promoting Effect of Slit3 <2-1> Confirmation of Change in Viability of Myoblasts by Slit3

Since it was confirmed that the amount of skeletal muscle was decreased according to Slit3 deficiency, it was confirmed what kind of role Slit3 played in increasing muscle mass. First, it was confirmed whether the role of Slit3 in increasing muscle mass is an effect of increasing the viability of muscle cells.

Specifically, a myoblast C2C12 cell line (purchased from ATCC, USA) was inoculated into a DMEM medium supplemented with 10% fetal bovine serum (FBS) and cultured while 5% CO₂ and 37° C. were maintained. After culturing for 24 hours, the cells were treated with recombinant Slit3 (manufactured by Abcam, Cambridge, Mass., USA; and R&D Systems Inc., Minneapolis, Minn., USA) at a concentration of 1 μg/ml or 3 μg/ml and additionally cultured for 24 hours. And then, the cells were washed twice with a PBS solution, treated with a MTT reagent, and then additionally cultured for 2 hours, and the absorbance was measured at 450 nm by an ELISA plate reader. As an untreated control group, a C2C12 cell line, which had not been treated with Slit3, was cultured under the same conditions, and as a positive control group, a C2C12 cell line treated with TNF-α was used.

As a result, as illustrated in FIG. 6, it was confirmed that in the positive control group treated with TNF-α, the cell viability was significantly increased as compared to that of the untreated control group, whereas in the experimental group treated with Slit3, the cell viability was not significantly changed.

<2-2> Confirmation of Differentiation-Increasing Effect of Slit3 in Differentiation from Myoblasts into Myotubes

Since it was confirmed that the amount of skeletal muscle was decreased according to Slit3 deficiency, it was confirmed what kind of role Slit3 played in increasing muscle mass. Since there was no significant change in the survival of myoblasts by Slit3, the effects of Slit3 on the differentiation process of myoblasts into myotubes were confirmed.

Specifically, C2C12 cells were inoculated into a DMEM medium supplemented with 10% FBS and cultured until 100% confluence. And then, the C2C12 cells were induced so as to be differentiated into myotubes by exchanging the culture medium with a DMEM medium including 1 μg/ml Slit3 recombinant protein and 2% horse serum. After the induction, the differentiated cells were obtained, treated with phosphate buffered saline (PBS), fixed at room temperature for 15 minutes, and treated with 0.1% Triton X-100 to impart permeability to the cell membrane. And then, the treated cells were blocked at room temperature for 1 hour by adding 4% normal donkey serum to the treated cells, and then treated with an anti-myosin heavy chain (MyHC) antibody as a primary antibody and cultured at 4° C. overnight, and washed several times with PBST that is a PBS including 0.1% Tween-20. After the washing, the cells were treated with a secondary antibody to which Alexa Fluor 594 bound and cultured for 1 hour, and MyHC was subjected to immunocytochemistry (ICC) staining. And then, the nuclei of the cells were stained by treating the cells with DAPI, and the stained nuclei were observed with a fluorescence microscope.

As a result, as illustrated in FIG. 7, it was confirmed that in the experimental group differentiated under the treatment of Slit3, the number of cells was not changed as compared to the untreated control group to which a Slit3 recombinant protein had not been added, but the area of the muscle fiber was significantly increased, and the fusion index was remarkably increased (FIG. 7).

Example 3 Confirmation of Slit3 Associated Factors in Differentiation Process of Myoblasts

Since it is known that various myogenic regulatory factors (MRFs) such as Myf5, Mrf4, MyoD, myogenin, Mef2A, and Mef2c cause differentiation of myoblasts in the process in which myoblasts are differentiated into myotubes, it was confirmed whether Slit3 induced differentiation of myoblasts by inducing the expression of these regulatory factors.

Specifically, after the C2C12 cells were inoculated into a DMEM supplemented with 10% FBS and cultured until 100% confluence, the C2C12 cells was induced so as to be differentiated into myotubes by exchanging the culture medium with a DMEM medium including 1 μg/ml Slit3 recombinant protein and 2% horse serum and culturing the cells for a total of 5 days. The cells were obtained every 24 hours while being cultured, and suspended in a TRIzol (Invitrogen, USA) reagent, and the total RNA of the differentiated myotubes was extracted according to the manufacturer's protocol and reverse-transcribed by employing 1 μg of RNA as a template and using the corresponding primer and superscript III kit (manufactured by Invitrogen, Inc., USA) to synthesize each of cDNAs of Myf5, Mrf4, MyoD, myogenin, Mef2A, and Mef2c. The amplification conditions for synthesis consisted of 30 cycles of denaturation at 95° C. for 30 seconds, annealing at 60° C. for 30 seconds, and extension at 72° C. for 30 seconds. For the synthesized cDNAs, it was confirmed that the expression level of myogenic regulatory factors was changed according to the presence or absence of treatment of Slit3 in myoblasts induced into differentiation by using a Light Cycler 480 SYBR Green I Master Mix (Roche) and carrying out real-time PCR in a Light Cycler 480 (Roche) apparatus under the conditions of an entire reaction at 95° C. for 10 minutes and 45 cycles of an amplification reaction which is a set of 95° C. for 10 seconds, 55° C. for 15 seconds, and 72° C. for 20 seconds.

Furthermore, the C2C12 cells induced into differentiation for 2 days were obtained, and the expression was confirmed at the protein level by subjecting myogenin induced into an increase in expression by Slit3 to fluorescence immunostaining in the cells induced into differentiation by using an anti-myogenin antibody in the same manner as in Example <2-2>.

As a result, as illustrated in FIGS. 8 to 10, it was confirmed that Slit3 did not exhibit a significant change in the expression of Myf5, Mrf4, MyoD, Mef2A, Mef2c, and the like, but the expression level of mRNA of myogenin was remarkably increased in the experimental group treated with Slit3, and exhibited a level increased about 1.8 times as compared to the expression level of myogenin mRNA in the untreated control group. Further, when the expression level of the myogenin protein was confirmed by fluorescence immunostaining, it was shown that in the experimental group treated with Slit3, the number of myogenin-positive cells were remarkably increased as compared to that in the untreated control group (FIGS. 9 and 10), so that it was confirmed that Slit3 could cause muscles to be formed by increasing the expression of myogenin to promote the differentiation of myoblasts.

Example 4 Confirmation of Myoblast Differentiation-Inducing Effect of Slit3 by β-Catenin Activation <4-1> Confirmation of Types and Expression Levels of Cadherin Proteins in Myoblasts

A receptor of a Slit protein is well known as a Robo protein which is a cell membrane protein. The Robo protein is present in the form of binding to a cadherin in the cell membrane, and it is known that when Slit binds to Robo, the binding between Robo and the cadherin becomes wider, and as a result, β-catenin binding to the cadherin migrates into the cells and is activated. Since the cadherins expressed in myoblasts are N-cadherin and M-cadherin, it was confirmed what type of cadherin could be affected by Slit3 by being associated with a Robo protein in myoblasts.

Specifically, a C2C12 cell line and a HEK297 cell line (kidney cell line) were inoculated into a DMEM medium supplemented with 10% FBS and cultured while 5% CO₂ and 37° C. were maintained. After culturing for 24 hours, each cell and brain tissue were obtained, and the expression levels of mRNAs of M-cadherin and N-cadherin were confirmed in the C2C12 cells and the HEK293 cells or brain tissues by carrying out real-time PCR in the same manner as in <Example 3>.

Further, a lysis buffer (20 mM Tris [pH 7.5], 150 mM NaCl, 1 mM EDTA, 1% Triton X-100, 2.5 mM sodium pyrophosphate, 1 mM glycerophosphate, 1 mM Na₃VO₄, 1 mM NaF, and a protease-inhibitor mixture) was mixed with each of the cells obtained above, a cell lysate was prepared by reacting the resulting mixture at 4° C. for 20 minutes, and the concentration of the protein in the lysate was confirmed by using a BCA protein analysis kit (Pierce Chemical Co., Rockford, Ill., USA). The cell lysate sample including 10 to 20 μg of the protein was isolated by a 10% gel SDS-PAGE, and then was transferred to a nitrocellulose membrane (Amersham Biosciences, Buckinghamshire, UK). And then, after the cells on the membrane were treated with a TBST buffer solution (500 mM Tris-HCL [pH 7.4], 1.5 M NaCl, 0.1% Tween-20) including 5% skimmed milk and blocked at room temperature for 1 hour, the cells were treated with an anti-M-cadherin antibody or an anti-N-cadherin antibody as a primary antibody and cultured at 4° C. overnight, washed with TBST, treated with TBST including 1% bovine serum albumin (BSA) by using a goose anti-mouse IgG antibody as a secondary antibody, and cultured for 1 hour to carry out a Western blot.

As a result, as illustrated in FIGS. 11A and 11B, it was confirmed that in the C2C12 cells, the expression level of mRNA of M-cadherin was significantly higher than that of N-cadherin (FIG. 11A), and it was confirmed that even in the expression level of proteins, the expression of the protein of M-cadherin is remarkably higher than that of N-cadherin (FIG. 11B).

<4-2> Confirmation of β-Catenin Activity in Myoblasts According to Addition of Slit3

Since it is known that Slit proteins activate β-catenin and β-catenin also binds to a promoter site of myogenin to promote the differentiation of myoblasts by increasing the expression of myogenin, in the present invention, it was also confirmed whether the β-catenin activity of myoblasts is changed by Slit3.

Specifically, the C2C12 cells were transfected with a β-catenin expression vector including a β-catenin-luciferase (luc) reporter gene. And then, after the transfected C2C12 cells were inoculated into a DMEM medium supplemented with 10% FBS and cultured until 100% confluence, the culture medium was exchanged with a DMEM medium including 1 μg/ml Slit3 recombinant protein and 2% horse serum, and a cell protein was extracted by suspending the cultured C2C12 cells in a reporter lysis buffer. The activity of the β-catenin-luciferase was confirmed by mixing a luciferase substrate (manufactured by Promega Corporation, USA) with 10 μl of the extracted cell protein and measuring luminescence with a luminometer.

As a result, as illustrated in FIG. 12A, it was confirmed that Slit3 increased the activity of the β-catenin-luciferase in myoblasts to a level of about 1.5 times as compared to the untreated control group (FIG. 12A).

<4-3> Confirmation of Changes in Binding Levels of M-Cadherin and β-Catenin According to Slit3 Treatment

Through the fact that the activity of β-catenin is high when C2C12 cells are treated with Slit3, since it was confirmed that Slit3 might bind to a Robo receptor to increase the activity of β-catenin and in the C2C12 cells, the expression level of M-cadherin was higher than the expression level of N-cadherin, it was confirmed by co-immunoprecipitation whether the binding between M-cadherin and β-catenin was changed according to the Slit3 treatment.

Specifically, a human cDNA of a GFP-tagged M-cadherin was purchased, the C2C12 cells were transformed with Lipofectamine 2000 (Gibco, Grand Island, N.Y., USA), and then treated with 1 μg/ml recombinant Slit3 to culture the cells. And then, the cultured cells were obtained and lysed with a TNE buffer (25 mM Tris-HCl, pH 7.4, 150 mM NaCl, 1% Triton X-100, 1 mM EDTA) including a protease inhibitor cocktail (Sigma-Aldrich, St. Louis, Mo., USA) and phosphatase inhibitors (1 mM Na₃VO₄, 1 mM NaF). The lysate was immunoprecipitated with an M-cadherin antibody and IgG at 4° C. for 30 minutes, and a Western blot was carried out by using an anti-β-catenin antibody in the same manner as in Example <4-1>.

As a result, as illustrated in FIG. 12B, it was confirmed that in the experimental group treated with Slit3, the level of β-catenin binding to M-cadherin was remarkably decreased, so that through Slit3, the binding between M-cadherin and a Robo protein became wider, and as a result, it was confirmed that β-catenin could also be released from M-cadherin to increase its activity (FIG. 12B).

<4-4> Confirmation of Difference in Effect of Slit3 in Promotion of Differentiation of Myoblasts According to Presence or Absence of Expression of β-Catenin

Since it was confirmed that β-catenin participated in the process in which Slit3 promoted the differentiation of myoblasts, it was confirmed whether the difference in effects of forming muscles occurred according to the presence or absence of expression of β-catenin when Slit3 was treated.

Specifically, after C2C12 cells were cultured in a DMEM including 10% FBS, a Lipofectamine 200 (Invitrogen) mixture including siRNA (CTNNB1 siRNA) of β-catenin was added thereto, and then the C2C12 cells were further cultured for additional 6 hours. After the culturing, the culture medium was exchanged with a fresh DMEM medium, and C2C12 cells in which β-catenin was knocked out were prepared by additionally culturing the cultured cells for 2 days. In order to be used as a normal control group expressing β-catenin, normal control group cells were prepared by transforming scrambled SiRNA instead of CTNNB1 siRNA.

And then, the prepared β-catenin knockout C2C12 cells or normal control group cells were inoculated into a DMEM medium supplemented with 10% FBS and cultured until 100% confluence, and then cultured by exchanging the culture medium with a DMEM medium including 1 μg/ml Slit3 recombinant protein and 2% horse serum. After the culture, cells were obtained and subjected to immunocytochemistry (ICC) staining in the same manner as in Example <2-2> by using an anti-MyHC antibody as a primary antibody. And then, the nuclei of the cells were stained by treating the cells with DAPI, and the number of cells was quantified as a fluorescence value by observing the stained nuclei with a fluorescence microscope. Fusion index (%) was denoted as a percentage of the number of nuclei of MyHC-expressing myotubes relative to the number of nuclei of the overall MyHC-expressing cells. Further, after the culture, the obtained cells were subjected to Western blot in the same manner as in Example <4-1> by using an anti-myogenin antibody.

As a result, as illustrated in FIGS. 12C to 12E and FIG. 12F, it was confirmed that in the experimental group in which the expression of β-catenin was suppressed by β-catenin siRNA, the hypertrophy of muscle fibers promoted by Slit3 and fusion index were remarkably suppressed, and it was confirmed that the expression of myogenin was also remarkably decreased (FIGS. 12C to 12E and FIG. 12F). Through this, it was confirmed that Slit3 released β-catenin binding to M-cadherin to activate β-catenin of myoblasts and increase the expression of myogenin, and could participate in promotion of the formation of muscles by inducing the differentiation of myoblasts.

Example 5 Confirmation of Robo Receptor Subtype Binding to Slit3 in Myoblasts <5-1> Confirmation of Robo Receptor Subtype Expressed in Myoblasts

It was confirmed that in the differentiation process of myoblasts, Slit3 could increase the activity of β-catenin and the expression of myogenin, and it was confirmed that the increase in activity of β-catenin and expression of myogenin could be induced through Slit3-Robo receptor binding. The receptor of the Slit protein is a Robo protein, and it has been known until now that four subtypes of Robo1 to Robo4 are present, so that the Robo receptor expressed in myoblasts was confirmed in order to confirm the subtype of Robo receptor associated with Slit3 in myoblasts.

Specifically, a C2C12 cell line and a HEK297 cell line (kidney cell line) were inoculated into a DMEM medium supplemented with 10% FBS and cultured while 5% CO₂ and 37° C. were maintained. After culturing for 24 hours, each cell was obtained, and the expression levels of proteins of Robo1, Robo2, Robo3, and Robo4 were confirmed in the C2C12 cells and the HEK293 cells or brain tissues by carrying out Western blot using an anti-Robo1 antibody, an anti-Robo2 antibody, an anti-Robo3 antibody, and an anti-Robo4 antibody in the same manner as in <Example 4>.

As a result, as illustrated in FIG. 13A, it was confirmed that in the C2C12 cells, Robo1 and Robo2 proteins were expressed at a significant level, but Robo3 and Robo4 proteins were not expressed (FIG. 13A).

<5-2> Confirmation of Binding of Slit3-Robo1 and Slit3-Robo2 in Myoblasts

Since it was confirmed that Robo1 and Robo2 proteins were expressed in myoblasts, it was determined whether the receptors of Slit3 protein could be Robo1 and Robo2. In order to confirm that the receptors of Slit3 protein are Robo1 and Robo2, it was confirmed whether the action of Slit3 was lost when the expression of Robo1 and Robo2 was suppressed.

Specifically, C2C12 cells in which Robo1 or Robo2 was knocked out were prepared by carrying out the same method as in Example <4-4> to transform the cells with each of siRNA of Robo1 or Robo2, the C2C12 cells were inoculated into a DMEM medium supplemented with 10% FBS and cultured until 100% confluence, and then cultured by exchanging the culture medium with a DMEM medium including 1 μg/ml Slit3 recombinant protein and 2% horse serum. After the culture, the cells were obtained, and when the expression of Robo1 and Robo2 was expressed, the mRNA expression levels of Robo1, Robo2, and myogenin were confirmed by carrying real-time PCR in the same manner as in <Example 3>.

As a result, as illustrated in FIGS. 13B and 13C, it was confirmed that for myogenin of which the expression was increased by Slit3, the expression of myogenin was significantly suppressed as the expressions of Robo1 and Robo2 are suppressed, and as a result, myogenin was expressed at a level similar to that of the control group which was not treated with Slit3 (FIGS. 13B, 13C, and 13D).

Example 6 Confirmation of Role of Robo Receptor in In Vivo Muscle Formation-Promoting Effect by Slit3

In order to specifically confirm the result confirmed in the present invention in vivo, a change in muscle mass was confirmed in a Robo receptor-deficient mouse model.

Specifically, embryos of Robo1 or Robo2 knockout mice were purchased from Mutant Mouse Regional Resource Centers (Stock number 030759-MU; Columbia, Mo., USA), and a Robo1 or Robo2 knockout mouse model was each prepared by breeding the male and female slit3+/−C57BL/6J mice. By selecting male mice as an experimental group among the mice, the body weights, muscle weights and sarcopenic indices of the 7 week-old mouse model were confirmed in the same manner as in Example <1-1>. The Robo2-deficient group did not survive until week 7 and could not be used as an experimental group, and the experiment was carried out only on the Robo1-deficient group, and the Robo1-deficient group was compared with the normal control group.

As a result, as illustrated in the following [Table 3] and FIG. 14, it was confirmed that in the Robo1-deficient mouse model, the body weights were lower and the weights of EDL and the weights of GC+SOL were also lower than those in the normal control group mice, and sarcopenic indices of EDL and sarcopenic indices of GC+SOL were significantly decreased as compared to those in the normal control group (FIG. 14 and Table 3). Through this, it was confirmed that the receptors of myoblasts participating in the formation of the skeletal muscle are Robo1 and Robo2, and Slit3 exhibits a decrease in muscle mass at the in vivo level, particularly when Robo1 is deficient, and accordingly, effects of alleviating sarcopenia could be exhibited through a binding system of Slit3 and Robo1 or Robo2.

TABLE 3 Comparison of Changes in Body Weight and Sarcopenic Indices in Robo1-Deficient Male Mice Experimental Body Muscle weight (g) Sarcopenic index (%) group weight (g) EDL GC + SOL EDL GC + SOL Normal 21.1 ± 0.048 ± 0.117 ± 0.206 ± 0.541 ± control 0.6 0.002 0.001 0.009 0.014 group Robo1- 17.6 ± 0.029 ± 0.085 ± 0.162 ± 0.474 ± deficient 0.9 0.003 0.002 0.011 0.024 group

Example 7 Confirmation of Effects of Slit3 on Differentiation of Myoblasts and Increase in Muscle Mass by LRRD2 Domain

Since a human Slit3 protein consists of 1,523 amino acids, and thus is a material having a very large molecular weight of about 170 kDa, it is determined that a medicine using a full-length Slit3 protein is not highly practical, so that it was intended to select only a domain fragment which was determined to exhibit effects of differentiation of myoblasts and an increase in muscle mass among the full-length Slit3. The Slit3 protein includes four Leucine-rich domains, and among the domains, Leucine-rich domain 2 (LRRD2) consisting of 130 amino acids is a portion which binds to the receptor, and through this, it was determined that various cellular actions could be performed, so that it was confirmed whether LRRD2 could exhibit the effects of the full length Slit3 even in effects of promoting differentiation of myoblasts of the present invention and increasing muscle mass.

<7-1> Confirmation of Effects of Slit3 on Differentiation of Myoblasts by LRRD2 at In Vitro Level

Specifically, after C2C12 cells were inoculated into a DMEM medium supplemented with 10% FBS and cultured until 100% confluence, the cells were cultured by exchanging the culture medium with a DMEM medium including 10 nM recombinant LRRD2 (Patent Document 1) and 2% horse serum. After the culture, cells were obtained and subjected to immunocytochemistry (ICC) staining in the same manner as in Example <2-2> by using an anti-MyHC antibody as a primary antibody. And then, the nuclei of the cells were stained by treating the cells with DAPI, and the number of cells was quantified as a fluorescence value by observing the stained nuclei with a fluorescence microscope. Fusion index (%) was denoted as a percentage of the number of nuclei of MyHC-expressing myotubes relative to the number of nuclei of the overall MyHC-expressing cells.

As a result, as illustrated in FIG. 15, it was confirmed that in the experimental group treated with the recombinant LRRD2 protein, the area of myotubes and fusion index levels were remarkably increased as compared to the untreated control group, which exhibited a level similar to that of the case where the full-length Slit3 protein was treated (FIG. 15).

<7-2> Confirmation of Effects of Slit3 on Increases in Body Weight and Sarcopenic Index by LRRD2

Specifically, a sarcopenia mouse model in which sex hormones were induced to be deficient was prepared by cutting the abdomens of 8 week-old female C57BL/6 mice open and excising the ovaries, and the recombinant LRRD2 domain was administered at a dosage of 2 μg or 10 μg and a frequency of once a day or five times a week intravenously to the sarcopenia mouse model. After 4 weeks, the body weights, muscle weights and sarcopenic indices of the 13 week-old mouse model were confirmed in the same manner as in Example <1-1>.

As a result, as shown in the following [Table 4] and FIG. 16, it was confirmed that the body weights of the mouse model to which LRRD2 was administered did not exhibit a significant change as compared to the control group to which LRRD2 was not administered, but with respect to muscle mass and sarcopenic index, in the mouse model to which LRRD2 was administered, the weights of EDL and the weights of GC+SOL were significantly increased as compared to the control group to which LRRD2 was not administered, and the sarcopenic indices of EDL and the sarcopenic indices of GC+SOL were also significantly increased as compared to the control group to which LRRD2 was not administered (FIG. 16 and Table 4).

TABLE 4 Comparison of Sarcopenic Indices by LRRD2 in Ovary-Excised Female Mice Muscle weight (g) Sarcopenic index (%) Experimental group EDL GC + SOL EDL GC + SOL Normal control group 0.040 ± 0.109 ± 0.196 ± 0.540 ± 0.001 0.003 0.006 0.017 LRRD2  2 μg 0.041 ± 0.121 ± 0.200 ± 0.596 ± treatment 0.005 0.001 0.010 0.011 group 10 μg 0.047 ± 0.119 ± 0.235 ± 0.594 ± 0.002 0.002 0.013 0.015 

The invention claimed is:
 1. A method for treating a muscle disease caused by decrease in differentiation of myoblast into myotube, muscle wasting or muscle degeneration, the method comprising the steps of: administering one protein selected from a group consisting of amino acid sequences of the following SEQ ID Nos. 1 and 4, or a gene encoding the same to an individual in need thereof: a Slit3 protein consisting of an amino acid of SEQ ID No. 1; and a LRRD2 protein domain consisting of an amino acid of SEQ ID No.
 4. 2. A method for improving muscular function in a muscle disease caused by decrease in differentiation of myoblast into myotube, muscle wasting or muscle degeneration, the method comprising the steps of: administering one protein selected from a group consisting of amino acid sequences of the following SEQ ID Nos. 1 and 4, or a gene encoding the same to an individual in need thereof: a Slit3 protein consisting of an amino acid of SEQ ID No. 1; and a LRRD2 protein domain consisting of an amino acid of SEQ ID No.
 4. 3. A method for treating a muscle disease caused by Robo1 or Robo2 deficiency, the method comprising the steps of: administering a gene encoding one protein selected from a group consisting of amino acid sequences of the following SEQ ID Nos. 2 and 3 to an individual in need thereof: a Robo1 protein consisting of an amino acid of SEQ ID No. 2; and a Robo2 protein consisting of an amino acid of SEQ ID No.
 3. 4. A method for improving muscular function in a muscle disease caused by Robo1 or Robo2 deficiency, the method comprising the steps of: administering a gene encoding one protein selected from a group consisting of amino acid sequences of the following SEQ ID Nos. 2 and 3 to an individual in need thereof: a Robo1 protein consisting of an amino acid of SEQ ID No. 2; and a Robo2 protein consisting of an amino acid of SEQ ID No.
 3. 